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1.
Stomatal movement in response to long distance-communicated signals initiated by heat shock in partial roots of Commelina communis L. 总被引:1,自引:0,他引:1
Songjie Yang Conglin Huang Zhongyi Wu Jianfang Hu Tianzhong Li Shigui Liu Wensuo Jia 《中国科学:生命科学英文版》2006,49(1):18-25
The systematic or long-distance signal transmission plays crucial roles in animal lives. Compared with animals, however, much less is known about the roles of long-distance signal communication in plant lives. Using the model plant Commelina communis L., we have probed the root to shoot communication mediated by heat-shock signals. The results showed that a heat shock of 5 min at 40℃ in partial roots, i.e. half or even 1/4 root system, could lead to a significant decrease in stomatal conductance. The regulation capability depends on both heat shock temperature and the amount of root system, i.e. with higher temperature and more roots stressed, the leaf conductance would decrease more significantly. Interestingly, the stomatal regulation by heat shock signal is in a manner of oscillation: when stomata conductance decreased to the lowest level within about 30 min, it would increase rapidly and sometimes even exceed the initial level, and after several cycles the stomata conductance would be finally stabilized at a lower level. Feeding xylem sap collected from heat-shocked plants could lead to a decrease in stomata conductance, suggesting that the heat shock-initiated signal is basically a positive signal. Further studies showed that heat shock was not able to affect ABA content in xylem sap, and also, not able to lead to a decrease in leaf water status, which suggested that the stomatal regulation was neither mediated by ABA nor by a hydraulic signal. Heat shock could lead to an increase in xylem sap H2O2 content, and moreover, the removal of H2O2 by catalase could partially recover the stomatal inhibition by xylem sap collected from heat-shocked plants, suggesting that H2O2 might be able to act as one of the root signals to control the stomatal movement. Due to the fact that heat-shock and drought are usually two concomitant stresses, the stomatal regulation by heat-shock signal should be of significance for plant response to stresses. The observation for the stomatal regulation in an oscillation manner by presently identified new signals should contribute to further understanding of the mystery for the pant systematic signaling in response to stresses. 相似文献
2.
Hydroponic-grown seedlings of aspen (Populus tremuloides Michx.) were used to investigate how low root temperatures (5°C) affect stomatal conductance and water relations. An isohydric manner of the stomatal behaviour was found with the seedlings when their roots were subjected to the low temperature. Stomatal conductance rapidly and dramatically reduced in response to the low root temperature, while the xylem water potential did not significantly alter. Under the low root temperature, pH value of the xylem sap increased from 6.15 to 6.72 within the initial 4 h, while abscisic acid (ABA) concentration increased by the eighth hour of treatment. K+ concentration of the xylem sap significantly decreased within the 8th h and then reversed by the 24th h. The ion change was accompanied by a decrease and then an increase in the electrical conductivity, and an increase and then a decrease in the osmotic potential. The tempo of physiological responses to the low root temperature suggests that the rapid pH change of the xylem sap was the initial factor which triggered stomatal closure in low temperature-treated seedlings, and that the role of the more slowly accumulating ABA was likely to reinforce the stomatal closure. Xylem sap from the seedlings subjected low root temperature affected stomatal aperture on leaf discs when they were floated on the sap solution. The stomatal aperture correlated (P = 0.006) with the changed pattern of [K+] in the sap while the range of pH or ABA found in the xylem sap did not influence stomatal aperture of leaf discs in solution. The effect of xylem sap on stomatal aperture on leaf discs was different from on stomatal conductance in the intact seedlings. Comparison was made with previous study with the soil-grown seedlings. 相似文献
3.
Drought-induced increase in xylem malate and mannitol concentrations and closure of Fraxinus excelsior L. stomata 总被引:4,自引:0,他引:4
Changes in the malate and mannitol composition of ash leaf
(Fraxinus excelsior L.) xylem sap were studied in
response to water deficit. Xylem sap was collected by the pressure method
from the petiole of leaves sampled on irrigated and non-irrigated ash
seedlings. As the leaf water potential decreased from -0.3 to -3.0 MPa,
there was a significant increase in malate and mannitol xylem
concentrations, and a concomitant decrease in maximal stomatal conductance.
The functional significance of the increased malate and mannitol
concentrations was investigated by using a transpiratory bioassay with
mature detached leaves which exhibited, for stomatal conductance, the
typical pattern showed by expanded leaves during dark/light transitions.
Supplying detached leaves with mannitol in a range of concentrations found
in the xylem sap had no effect on stomatal movements, but malate, for
concentrations between 0.5 and 3 mM, was effective in preventing stomatal
opening. The ability of malate to inhibit stomatal opening appeared to be
rather non-specific. Two structural malate analogues, citrate and aspartate
or an unrelated anion, shikimate, also inhibited this process. Given the
drought-induced increase in xylem malate concentrations, and the fact that
the range of malate levels required to close stomata was very similar to
that of the concentrations found in the xylem sap, it has been hypothesized
that malate is involved in the stomatal closure of ash leaves under drying
conditions.Key words: Fraxinus excelsior: L., malate,
mannitol, xylem sap, stomata, water deficit.
相似文献
4.
Understanding the regulation of calcium uptake, xylem transport and its impacts on growth and leaf gas exchange is a subject that has received insufficient recent attention. Calcium (Ca) is unique within the group of key elements required for plant growth in that it also has a role in cellular signalling via regulation of changes in its cytoplasmic concentration. Its mobility, within the plant, is however somewhat constricted by its chemistry and cellular signalling role, and its adsorptive capacity within the aopoplast and the xylem. Supply and demand for Ca is achieved by a homeostatic balance which if perturbed can cause a number of distinctive physiological conditions, often related to Ca deficiency. In this issue Rothwell and Dodd present experiments with bean (Phaseolus vulgaris) and pea (Pisum sativum) plants grown in a field soil exposed to the processes of soil liming (application of Ca carbonate (CaCO3). Given that there is evidence of free Ca in the xylem sap altering stomatal conductance it is reasonable to ask the question does liming elevate Ca in the transpiration stream which may explain the observed reduced growth which they hypothesise is due to Ca-induced stomatal closure. They show that liming doubled soil exchangeable Ca, reduced stomatal conductance and shoot biomass in both species compared with unlimed controls. However, xylem sap Ca concentration increased only in bean. Interestingly, the same was not true for the pea where the root xylem sap concentration remained unchanged despite an increase in soil available Ca. Given that stomatal conductance decreased in both species, but in response to a lime-induced increase in xylem sap Ca in only one; this questions the role of Ca in inducing stomatal closure. They propose that their data suggest that as yet unidentified antitranspirant causes stomatal closure in both species not the increase in xylem sap Ca per se. 相似文献
5.
Does Xylem Sap ABA Control the Stomatal Behaviour of Water-Stressed Sycamore (Acer pseudoplatanus L.) Seedlings? 总被引:3,自引:0,他引:3
Sycamore seedlings were grown with their root systems dividedequally between two containers. Water was withheld from onecontainer while the other container was kept well-watered. Effectsof soil drying on stomatal behaviour, shoot water status, andabscisic acid (ABA) concentration in roots, xylem sap and leaveswere evaluated. At 3 d, root ABA in the drying container increased significantly,while the root ABA in the unstressed container of the same plantsdid not differ from that of the control. The increase in rootABA was associated with the increase in xylem sap ABA and withthe decrease in stomatal conductance without any significantperturbation in shoot water status. At 7 d, despite the continuous increase in root ABA concentration,xylem sap ABA showed a marked decline when soil water contentwas depleted below 013 g g1. This reduction in xylemsap ABA coincided with a partial recovery of stomatal conductance.The results indicate that xylem sap ABA is a function of rootABA as well as the flow rate of water from roots to shoots,and that this ABA can be a sensitive indicator to the shootof the effect of soil drying. Key words: Acer pseudoplatanus L., soil drying, stomatal behaviour, xylem sap ABA 相似文献
6.
Diurnal change in the relationship between stomatal conductance and abscisic acid in the xylem sap of field-grown peach trees 总被引:3,自引:0,他引:3
Correia M.J.; Rodrigues M.L.; Ferreira M.I.; Pereira J.S. 《Journal of experimental botany》1997,48(9):1727-1736
To evaluate whether abscisic acid (ABA) in the xylem sap playsan important role in controlling stomatal aperture of field-grownPrunus persica trees under drought conditions, stomatal conductance(g) and xylem ABA concentrations were monitored both in irrigatedand non-irrigated trees, on two consecutive summer days (threetimes a day). Stomata1 conductance of non-irrigated trees hada morning maximum and declined afterwards. The changes in gduring the day, rather than resulting from variations in theconcentrations of ABA in the xylem sap or the delivery rateof this compound to the leaves, were associated with changesin the relationship between g and xylem ABA. The stomata ofwater-stressed trees opened during the first hours of the day,despite the occurrence of a high concentration of ABA in thexylem sap. However, stomatal responsiveness to ABA in the xylemwas enhanced throughout the day. As a result, a tight inverserelationship between g and the logarithm of xylem ABA concentrationwas found both at midday and in the afternoon. A similar relationshipbetween g and ABA was found when exogenous ABA was fed to leavesdetached from well-watered trees. These results indicate thatABA derived from the xylem may account for the differences ing observed between field-grown peach trees growing with differentsoil water availabilities. Several possible explanations forthe apparent low stomatal sensitivity to xylem ABA in the morning,are discussed, such as high leaf water potential, low temperatureand high cytokinin activity. Key words: Prunus persica L., stomata, xylem ABA, water deficits, root-to-shoot communication 相似文献
7.
Integration of hydraulic and chemical signalling in the control of stomatal conductance and water status of droughted plants 总被引:8,自引:0,他引:8
We describe here an integration of hydraulic and chemical signals which control stomatal conductance of plants in drying soil, and suggest that such a system is more likely than control based on chemical signals or water relations alone. The determination of xylem [ABA] and the stomatal response to xylem [ABA] are likely to involve the water flux through the plant. (1) If, as seems likely, the production of a chemical message depends on the root water status (Ψr), it will not depend solely on the soil water potential (Ψs) but also on the flux of water through the soil-plant-atmosphere continuum, to which are linked the difference between Ψr and Ψs. (2) The water flux will also dilute the concentration of the message in the xylem sap. (3) The stomatal sensitivity to the message is increased as leaf water potential falls. Stomatal conductance, which controls the water flux, therefore would be controlled by a water-flux-dependent message, with a water-flux-dependent sensitivity. In such a system, we have to consider a common regulation for stomatal conductance, leaf and root water potentials, water flux and concentration of ABA in the xylem. In order to test this possibility, we have combined equations which describe the generation and effects of chemical signals and classical equations of water flux. When the simulation was run for a variety of conditions, the solution suggested that such common regulation can operate. Simulations suggest that, as well as providing control of stomatal conductance, integration of chemical and hydraulic signalling may also provide a control of leaf water potential and of xylem [ABA], features which are apparent from our experimental data. We conclude that the root message would provide the plant with a means to sense the conditions of water extraction (soil water status and resisance to water flux) on a daily timescale, while the short-term plant response to this message would depend on the evaporative demand. 相似文献
8.
Inherent differences in the responses of stomata on abaxialand adaxial epidermal surfaces of leaves of Commelina communishave previously been suggested to be due to differences in theconcentrations of apoplastic Ca. Adaxial stomata have also beenreported to be more sensitive than abaxial stomata to appliedabscisic acid (ABA). The aims of these experiments were to determinethe validity of these conclusions and to see if xylem sap Cahas a role in determining the response of stomata to ABA. It can be shown from measurements of relative stomatal resistance(determined with a viscous flow porometer) and stomatal conductancethat stomata were more open in plants grown on 8-0 mol m3Ca, than with those grown on 2-0 mol m3 Ca. When attachedleaves were fed with ABA via the transpiration stream neitherthe extent nor the rate with which conductance declined wasdependent on Ca nutrition. The extent of Ca accumulation within both epidermes was relatedto the concentration of Ca in the rhizosphere and in the xylemsap. It did not, however, appear to reflect the apparent differencesin the flux of the transpiration stream between the two epidermes.Plants growing at the lower Ca concentration accumulated proportionallymore epidermal Ca relative to Ca in xylem sap. The evidencepresented suggests that Ca movement from the xylem to the epidermiscannot be simply described by a mass flow model, and that thedistribution of Ca is not an adequate explanation of the differencesin the behaviour of adaxial and abaxial stomata. The potentialrole for changes in xylem sap Ca to act as a regulator of stomatalbehaviour are discussed. Key words: Abscisic acid, calcium, Commelina communis L., stomatal conductance 相似文献
9.
We present the first study of abscisic acid (ABA) concentrations and fluxes in the xylem sap of conifers during a drought cycle. In both Pinus sylvestris and Picea sitchensis the concentration of ABA in the sap rose 11-fold as the drought progressed. There were clear diurnal trends in this concentration, which reached its maximum (6–8.ininol ABA m?3) near the middle of the day. The fluxes of ABA were calculated by multiplying the xylem ABA concentration by the sap flow rate. The ABA fluxes in the droughted plants in the middle of the day were usually no higher than those of the controls, as a result of the very low sap flow in the droughted plants at that time. However, the ABA flux in the droughted plants was higher than in the controls in the morning, and we postulate that the stomata are responding to these ‘morning doses’ Stomatal conductance, gs, could not be related statistically to leaf turgor or to the ABA flux. However, £s did display a negative exponential relationship with ABA concentration in the xylem. Pinus displayed more acclimation to drought than Picea, Its ABA concentration rose and its stomatal conductance fell at day 6 of the drought, as opposed to day 17 for Picea, and its osmotic potential fell during the drought treatment. 相似文献
10.
Juan Rodríguez‐Gamir Jianming Xue Michael J. Clearwater Dean F. Meason Peter W. Clinton Jean‐Christophe Domec 《Plant, cell & environment》2019,42(2):717-729
Stomatal regulation is crucial for forest species performance and survival on drought‐prone sites. We investigated the regulation of root and shoot hydraulics in three Pinus radiata clones exposed to drought stress and its coordination with stomatal conductance (gs) and leaf water potential (Ψleaf). All clones experienced a substantial decrease in root‐specific root hydraulic conductance (Kroot‐r) in response to the water stress, but leaf‐specific shoot hydraulic conductance (Kshoot‐l) did not change in any of the clones. The reduction in Kroot‐r caused a decrease in leaf‐specific whole‐plant hydraulic conductance (Kplant‐l). Among clones, the larger the decrease in Kplant‐l, the more stomata closed in response to drought. Rewatering resulted in a quick recovery of Kroot‐r and gs. Our results demonstrated that the reduction in Kplant‐l, attributed to a down regulation of aquaporin activity in roots, was linked to the isohydric stomatal behaviour, resulting in a nearly constant Ψleaf as water stress started. We concluded that higher Kplant‐l is associated with water stress resistance by sustaining a less negative Ψleaf and delaying stomatal closure. 相似文献
11.
Fambrini Marco; Pugliesi Claudio; Vernieri Paolo; Pardossi Alberto; Baroncelli Sergio 《Journal of experimental botany》1994,45(12):1809-1815
The response of w-1, a wilty sunflower (Helianthus annuus L.)mutant, to water stress is described in comparison with thecontrol line (W-1). Detached leaves of w-1 strongly dehydratedduring the first 30 min without significant changes in leafconductance, whereas W-1 responded rapidly to water loss byreducing stomatal aperture. After 2 h stress ABA increased slightlyin w-1, while W-1 leaves showed a 20-fold increase. When waterstress was imposed to potted plants by water withholding, w-1quickly dehydrated, and lost turgor, while W-1 maintained positiveturgor values for a longer period. Wild-type plants respondedto small changes in leaf water potential by accumulating ABAand by closing stomata, whereas in the mutant significant changesin ABA content and in stomatal conductance were found only atvery low water potentials. In another experiment in which waterwas withheld under high relative humidity, when soil water contentstarted to decrease W-1 rapidly closed stomata in the absenceof any change in leaf water status and the reduction in conductancewas paralleled by a rise in xylem sap ABA concentration. Bycontrast the mutant started to accumulate ABA in the xylem sapand to close stomata when soil water content and leaf waterpotential were dramatically reduced. The low endogenous ABAlevels and the inability to synthesize the hormone rapidly eitherin the leaves or in the roots seem to be responsible for thehigh sensitivity of w-1 to water stress. Key words: ABA, Helianthus annuus L, water relations, stomatal conductance, drought, wilty mutant 相似文献
12.
S. V. Veselova R. G. Farkhutdinov D. S. Veselov G. R. Kudoyarova 《Russian Journal of Plant Physiology》2006,53(6):756-761
The influence of an air temperature increase by 4°C and nutrient solution cooling down to 5 ± 1°C on stomatal conductance and hormone level of seven-day-old wheat (Triticum durum L., cv. Bezenchukskaya 139) seedlings was studied. An elevated air temperature resulted in a rapid rise of stomatal conductance preceded by the increase in the level of cytokinins in leaves. Cooling of the nutrient solution induced gradual stomatal closure along with a decreasing cytokinin level in leaves. Hormone concentration in the xylem sap of wheat seedlings was determined, and the rate of hormone transport from the roots to shoots was calculated. The role of cytokinins in the regulation of stomatal conductance under conditions of local thermal treatments is discussed. 相似文献
13.
Unraveling the Effects of Plant Hydraulics on Stomatal Closure during Water Stress in Walnut 总被引:14,自引:0,他引:14
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The objectives of the study were to identify the relevant hydraulic parameters associated with stomatal regulation during water stress and to test the hypothesis of a stomatal control of xylem embolism in walnut (Juglans regia x nigra) trees. The hydraulic characteristics of the sap pathway were experimentally altered with different methods to alter plant transpiration (Eplant) and stomatal conductance (gs). Potted trees were exposed to a soil water depletion to alter soil water potential (Psisoil), soil resistance (Rsoil), and root hydraulic resistances (Rroot). Soil temperature was changed to alter Rroot alone. Embolism was created in the trunk to increase shoot resistance (Rshoot). Stomata closed in response to these stresses with the effect of maintaining the water pressure in the leaf rachis xylem (P(rachis)) above -1.4 MPa and the leaf water potential (Psileaf) above -1.6 MPa. The same dependence of Eplant and gs on P(rachis) or Psileaf was always observed. This suggested that stomata were not responding to changes in Psisoil, Rsoil, Rroot, or Rshoot per se but rather to their impact on P(rachis) and/or Psileaf. Leaf rachis was the most vulnerable organ, with a threshold P(rachis) for embolism induction of -1.4 MPa. The minimum Psileaf values corresponded to leaf turgor loss point. This suggested that stomata are responding to leaf water status as determined by transpiration rate and plant hydraulics and that P(rachis) might be the physiological parameter regulated by stomatal closure during water stress, which would have the effect of preventing extensive developments of cavitation during water stress. 相似文献
14.
为探讨亚低温和干旱对植株水分传输的影响机制,以番茄幼苗为试材,利用人工气候室设置常温(昼25 ℃/夜18 ℃)和亚低温(昼15 ℃/夜8 ℃)环境,采用盆栽进行正常灌水(75%~85%田间持水量)和干旱处理(55%~65%田间持水量),分析了温度和土壤水分对番茄植株水分传输、气孔和木质部导管形态解剖结构的影响。结果表明: 与常温正常灌水处理相比,干旱处理使番茄叶水势、蒸腾速率、气孔导度、水力导度、茎流速率、气孔长度和叶、茎、根导管直径显著减小,而使叶、茎、根导管细胞壁厚度和抗栓塞能力增强;亚低温处理下番茄叶水势、蒸腾速率、气孔导度、水力导度和叶、茎、根导管直径显著降低,但气孔变大,叶、根导管细胞壁厚度和叶、茎、根抗栓塞能力显著升高。亚低温条件下土壤水分状况对番茄叶水势、蒸腾速率、气孔导度、水力导度、气孔形态、叶、根导管结构均无显著影响。总之,干旱处理下番茄通过协同调控叶、茎、根结构使植株水分关系重新达到稳态;亚低温处理下番茄植株水分关系的调控主要通过改变叶和根导管结构实现,且受土壤水分状况的影响较小。 相似文献
15.
Hydraulic conductance of stem and petioles increased in response to an increase in xylem sap ion concentration, and decreased
in response to a decrease in the ion concentration in six temperate deciduous tree species. The ion sensitivity of hydraulic
conductance of stem and petioles was higher than the ion sensitivity of the stem alone. The ion sensitivity was lowest in
the earliest developmental stages of the xylem, and had a seasonal maximum in the second half of summer. The ion sensitivity
was highest in slow-growing species and lowest in fast-growing species. The ion sensitivity correlated negatively with mean
radius of xylem conduits, hydraulic conductance of stem and petioles, hydraulic conductance of leaf laminae, and stomatal
conductance, and positively with response of the hydraulic conductance of leaf laminae to HgCl2, and stomatal response to a decrease in leaf water potential or abscisic acid. It was concluded that the high ion sensitivity
of xylem hydraulic conductance is a relevant characteristic of slow growth and a conservative water use strategy. 相似文献
16.
Does engineering abscisic acid biosynthesis in Nicotiana plumbaginifolia modify stomatal response to drought? 总被引:5,自引:1,他引:4
C. Borel A. Frey A. Marion-Poll F. Tardieu & T. Simonneau 《Plant, cell & environment》2001,24(5):477-489
The consequences of manipulating abscisic acid (ABA) biosynthesis rates on stomatal response to drought were analysed in wild‐type, a full‐deficient mutant and four under‐producing transgenic lines of N. plumbaginifolia. The roles of ABA, xylem sap pH and leaf water potential were investigated under four experimental conditions: feeding detached leaves with varying ABA concentration; injecting exogenous ABA into well‐watered plants; and withholding irrigation on pot‐grown plants, either intact or grafted onto tobacco. Changes in ABA synthesis abilities among lines did not affect stomatal sensitivity to ABA concentration in the leaf xylem sap ([ABA]xyl), as evidenced with exogenous ABA supplies and natural increases of [ABA]xyl in grafted plants subjected to drought. The ABA‐deficient mutant, which is uncultivable under normal evaporative demand, was grafted onto tobacco stock and then presented the same stomatal response to [ABA]xyl as wild‐type and other lines. This reinforces the dominant role of ABA in controlling stomatal response to drought in N. plumbaginifolia whereas roles of leaf water potential and xylem sap pH were excluded under all studied conditions. However, when plants were submitted to soil drying onto their own roots, stomatal response to [ABA]xyl slightly differed among lines. It is suggested, consistently with all the results, that an additional root signal of soil drying modulates stomatal response to [ABA]xyl. 相似文献
17.
The stomatal conductance of several anisohydric plant species, including field-grown sunflower, frequently correlates with leaf water potential (φ1), suggesting that chemical messages travelling from roots to shoots may not play an important role in stomatal control. We have performed a series of experiments in which evaporative demand, soil water status and ABA origin (endogenous or artificial) were varied in order to analyse stomatal control. Sunflower plants were subjected to a range of soil water potentials under contrasting air vapour pressure deficits (VPD, from 0.5 to 2.5 kPa) in the field, in the glasshouse or in a humid chamber. Sunflower plants were also fed through the xylem with varying concentrations of artificial ABA, in the glasshouse and in the field. Finally, detached leaves were fed directly with varying concentrations of ABA under three contrasting VPDs. A unique relationship between stomatal conductance (gs) and the concentration of ABA in the xylem sap (xylem [ABA]) was observed in all cases. In contrast, the relationship between φ1 and gs varied substantially among experiments. Its slope was positive for droughted plants and negative for ABA-fed whole plants or detached leaves, and also varied appreciably with air VPD. All observed relationships could be modelled on the basis of the assumption that φ1 had no controlling effect on gs. We conclude that stomatal control depended only on the concentration of ABA in the xylem sap, and that φ1 was controlled by water flux through the plant (itself controlled by stomatal conductance). The possibility is also raised that differences in stomatal ‘strategy’ between isohydric plants (such as maize, where daytime φ1 does not vary appreciably with soil water status) and anisohydric plants (such as sunflower) may be accounted for by the degree of influence of φ1 on stomatal control, for a given level of xylem [ABA]. We propose that statistical relationships between φ1 and gs are only observed when φ1 has no controlling action on stomatal behaviour. 相似文献
18.
The effect of root cooling on hormone content, leaf conductance and root hydraulic conductivity of durum wheat seedlings (Triticum durum L.) 总被引:2,自引:0,他引:2
Veselova SV Farhutdinov RG Veselov SY Kudoyarova GR Veselov DS Hartung W 《Journal of plant physiology》2005,162(1):162-26
Root cooling of 7-day-old wheat seedlings decreased root hydraulic conductivity causing a gradual loss of relative water content during 45 min (RWC). Subsequently (in 60 min), RWC became partially restored due to a decrease in transpiration linked to lower stomatal conductivity. The decrease in stomatal conductivity cannot be attributed to ABA-induced stomatal closure, since no increase in ABA content in the leaves or in the concentration in xylem sap or delivery of ABA from roots was found. However, decreased stomatal conductance was associated with a sharp decline in the content of cytokinins in shoots that was registered shortly after the start of root cooling and linked to increases in the activity of cytokinin-oxidase. This decrease in shoot cytokinin content may have been responsible for closing stomata, since this hormone is known to maintain stomatal opening when applied to plants. In support of this, pre-treatment with synthetic cytokinin benzyladenine was found to increase transpiration of wheat seedlings with cooled roots and bring about visible loss of turgor and wilting. 相似文献
19.
Hormonal Interactions and Stomatal Responses 总被引:18,自引:4,他引:14
Both environmental and hormonal factors and their interactions affect stomatal behavior. Methodologies for identifying hormonal interactions affecting stomatal function are reviewed. Although there is abundant evidence that abscisic acid (ABA) closes stomata, evidence that the other classical plant hormones (auxins, cytokinins, ethylene, gibberellins) in isolation alter stomatal response often comes from exogenous applications to detached epidermes and leaves, rather than correlation of endogenous concentrations with stomatal conductance (gs). Evidence for hormonal interactions comes from isolated tissues with exogenous hormones supplied at nonphysiological concentrations, or from variation in stomatal response to xylem ABA concentration in planta. The roles of hormonal changes in causing stomatal closure following changes in soil environment are considered. Although soil drying induces multiple changes in xylem sap composition, analysis of stomatal responses suggests a dominant role for increased endogenous ABA concentrations and relatively little evidence of roles for other hormones. A similar picture emerges from studies of soil compaction. Although soil flooding decreases ABA export from the root system, there is some evidence that apoplastic ABA accumulation elicits stomatal closure. Stomatal closure following nitrogen deprivation does not appear to involve ABA and may provide a suitable experimental system to investigate roles for other hormones. The availability of mutant or transgenic lines with altered hormone homeostasis or sensitivity provides opportunities to screen for altered stomatal behavior in response to different environments, and may provide new evidence that hormonal interactions are important in the control of stomatal behavior. 相似文献
20.
Water relations and hydraulic control of stomatal behaviour in bell pepper plant in partial soil drying 总被引:4,自引:0,他引:4
Two experiments, a split-root experiment and a root pressurizing experiment, were performed to test whether hydraulic signalling of soil drying plays a dominant role in controlling stomatal closure in herbaceous bell pepper plants. In the split-root experiment, when both root parts were dried, synchronous decreases in stomatal conductance (gs), leaf water potential (LWP) and stem sap flow (SFstem) were observed. The value of gs was found to be closely related to soil water potential (SWP) in both compartments. Tight relationships were observed between gs and stem sap flow under all conditions of water stress, indicating a complete stomatal adjustment of transpiration. When the half-root system has been dried to the extent that its water uptake dropped to almost zero, declines in gs of less than 20% were observed without obvious changes in LWP. The reduced plant hydraulic conductance resulting from decreased sap flow and unchanged LWP may be a hydraulic signal controlling stomatal closure; the results of root pressurizing supported this hypothesis. Both LWP and gs in water-stressed plants recovered completely within 25 min of the application of root pressurizing, and decreased significantly within 40 min after pressure release, indicating the hydraulic control of stomatal closure. Our results are in contrast to those of other studies on other herbaceous species, which suggested that chemical messengers from the roots bring about stomatal closure when plants are in water stress. 相似文献